KR20130143563A - A method for projecting an image - Google Patents

Abstract

According to the present invention, a method of projecting an image is provided, the method comprising: providing an optical signal configured to be projected on a display surface for displaying an image; And oscillating the first reflective surface to scan an optical signal across the display surface using an actuator operatively cooperating with the first reflective surface by applying the first drive signal to the first reflective surface; The rise time or fall time of one drive signal is inversely proportional to the resonant frequency of oscillation of the first reflective surface.

Description

How to project an image {A METHOD FOR PROJECTING AN IMAGE}

FIELD OF THE INVENTION The present invention relates to a method of projecting an image onto a display surface, and in particular to a method of projecting an image onto a display surface involving oscillating one or more mirrors to scan light projected over the display surface. Although not limited thereto, the oscillating drive signal shape of one or more mirrors is optimized to improve the quality of the image visible on the display surface.

MEMS micro-mirror devices are devices that include optical MEMS (Micro-Electrical-Mechanical-System). The light MEMS can include cylindrical, rectangular or square micromirrors adapted to move and deflect light over time. The micromirror is typically connected to the stationary portion by torsion arms and can be tilted and oscillated along one or two axes. Different driving principles can be used including electrostatic, thermal, electromagnetic or piezoelectric. MEMS micromirror devices are known in which the area of their micromirrors is about several mm ² . In this case, the dimensions of the MEMS device including the packaging are about 10 mm ² . The device is typically made of silicon and can be encapsulated in a package that can contain the driving electronics that drive. Various optical components such as lenses, beam combiners, quarter-wave plates, beam splitters and laser chips, for example, are assembled together with the MEMS packaged to build a complete system such as a projection system. do.

Typical applications of MEMS micromirror devices are for projection systems. In a projection system, a 2-D image or video can be displayed on the display surface; Each pixel of the 2-D image or video is produced by combining modulated red, green and blue laser light sources, for example by a beam combiner. The combined light from the modulated red, green and blue lasers is emitted from the beam combiner as a beam of light. The light beam emitted from the beam combiner includes pulses, each pulse corresponding to a pixel of a 2-D image or video. MEMS micromirror devices direct a beam of light onto the display surface so that 2-D images, or video, are displayed pixel-by-pixel on the display surface, and then zig-zag or recurse across the display surface. It is oscillated to scan the light beam in a lissajou pattern. The micromirror in the MEMS micromirror device will scan light continuously from left to right and from top to bottom so that each pixel of the 2-D image or video is reproduced continuously. The speed of the oscillating micromirror is such that a complete 2-D image or video is shown on the display surface.

Typically, the micromirror of the MEMS micromirror device may oscillate along one axis. Therefore, to display a 2-D image on the display surface, the projection system will require two MEMS micromirror devices; The first MEMS micromirror device is required to scan light along the horizontal, and the second MEMS micromirror device is required to scan light along the vertical. The first and second MEMS micromirror devices can be accurately arranged such that the oscillation axes of their respective micromirrors are orthogonal.

During operation, the micromirror of the first MEMS micromirror device receives light from the beam combiner and deflects the light to the micromirror of the second MEMS micromirror device. The micromirror of the second MEMS micromirror device will in turn deflect light onto the display surface, which appears as a pixel. The micromirror of the first MEMS micromirror device oscillates to scan light along a horizontal line to display a first row of pixels on the display surface pixel by pixel. When the first row of pixels has been projected onto the display surface, the micromirror of the second MEMS micromirror device is adapted such that light received from the micromirror of the first MEMS micromirror device is directed towards the next row where the pixels are displayed. Will move about the oscillation axis. The micromirror of the first MEMS micromirror device will then be oscillated to scan the light along the horizontal to mark the next row of pixels. The process is continuous so that a complete image is shown on the display surface. Typically, the rate of oscillation of the micromirror in the second MEMS micromirror device will be much slower than the rate of oscillation of the micromirror in the first MEMS micromirror device. Thus, the micromirror in the second MEMS micromirror device (ie the micromirror responsible for scanning light vertically) is often referred to as a 'slow mirror' and the micromirror in the first MEMS micromirror device ( The micromirror responsible for scanning light along the horizontal plane is often referred to as a 'fast mirror'.

It is also known to provide high speed and low speed micromirrors in the same MEMS micromirror device. Advantageously, in the case of such MEMS micromirror devices, the micromirrors are prearranged during the manufacturing step in the MEMS micromirror device such that their oscillating axes are orthogonal. A further advantage is that the projection system only requires one such MEMS micromirror device to display the 2-D image on the display surface.

Other MEMS micromirror devices include a single 2-D micromirror that can oscillate along two orthogonal oscillation axes. During operation, a single 2-D micromirror receives modulated light from the beam combiner and deflects the light onto the display surface, which appears as a pixel. A single 2-D micromirror will oscillate along the first oscillation axis to scan light horizontally, thereby displaying a first row of pixels on the display surface. When the first row of pixels has been projected onto the display surface, a single 2-D micromirror is directed against the second oscillation axis such that the light received from the beam combiner is directed towards the next row where the pixels are displayed (with the first oscillation axis and Orthogonal) oscillates. A single 2-D micromirror will display the next row of pixels on the display surface by oscillating along the first oscillation axis to scan light horizontally from the beam combiner. The process is continuous so that a complete image is shown on the display surface. It is also possible for the 2-D micromirror to oscillate simultaneously for both the first and second oscillation axes. The advantage of using a single 2-D micromirror that can oscillate along two orthogonal oscillation axes is that only a single micromirror is required to display a 2-D image on the display surface. Typically, the rate of oscillation of a single 2-D micromirror with respect to the first oscillation axis is much greater than the rate of oscillation of a single 2-D micromirror with respect to the second oscillation axis; Thus, the first oscillation axis (ie the axis from which a single 2-D micromirror oscillates to scan light along the horizontal) is known as the "fast axis" and the second oscillation axis (ie single 2-) The axis through which the D micromirror oscillates to scan light along a vertical line is known as the "slow axis".

The rate of oscillation of the micromirrors for each oscillation axis greatly affects the quality of the projected image seen on the display surface. For example, if a high speed mirror oscillates too fast about its oscillation axis, then the spacing between successive pixels on the display surface will be too large and the projected image will appear blurred on the display surface. Conversely, if the fast mirror oscillates too slowly about its oscillation axis, then successive superpositions of pixels may create on the display surface and the quality of the projected image visible on the display surface will be compromised.

Typically, a "high speed mirror" oscillates at its mechanical resonant frequency of oscillation, or in the case of a single 2-D micromirror it typically oscillates at its mechanical resonant frequency of oscillation about the "high speed axis". Therefore, the speed of oscillation of a single 2-D micromirror with respect to a "high speed mirror" or "high speed axis" can no longer be increased without compromising other characteristics (power consumption, scanning angle). In contrast, the speed of the oscillation of the "low speed mirror" and the speed of the oscillation of a single 2-D micromirror with respect to the "low speed axis" can be increased and manipulated.

The speed of oscillation of the "low speed mirror" preferably causes the slow mirror to oscillate very slowly so that light is scanned in a zigzag pattern across the display screen when the high speed mirror scans along a row.

The fast mirror and the slow mirror must continue to oscillate until each pixel of the 2-D image or video has been projected onto the display surface. The process of scanning light from a projector over the display surface is performed at a rate that ensures that a continuously repeated and complete image is shown on the display surface. Thus, if light from the projector has been scanned across the display surface to display each of the pixels of the 2-D image or video, the light from the projector can start the scanning process once again so that the projected image can be "played back". To be projected again towards the top of the image. In order to direct the light once more to the top of the image, the slow mirror must be oscillated to return to its original position. Preferably, the slow mirror should immediately oscillate back to its original position. Thus, ideally, the amplitude of the oscillation of the slow mirror should have a saw-tooth profile as shown in FIG.

Between the viewpoints A and B, the slow mirror oscillates slowly to scan light vertically along the display surface. The combination of the vertical scan provided by the slow mirror and the horizontal scan provided by the high speed mirror means that the light from the projector is scanned in a zigzag pattern across the display surface. Alternatively, the slow mirrors may be oscillated sequentially as shown in FIG. 2; In this case each row of pixels will be projected along a horizontal line row by row; A fast mirror is oscillated to scan light along a horizontal line to indicate a row of pixels; If a row of pixels has been projected, the slow mirror will be oscillated so that the projected light is directed to the next row where the pixels are displayed. The number of steps undertaken by the slow mirror will correspond to the number of rows forming the projected image; The number of steps is typically between approximately 240 and 1080.

Regardless of whether the slow mirror undergoes a constant slow oscillation movement or sequential oscillation, each pixel of the 2-D image or video at point B was projected onto the display surface. Thus, the slow mirror at B is immediately oscillated back to its original position so that the scanning process can be initiated once again from the first pixel of the 2-D image so that the projected image can be "played back".

In practice, however, due to the inertia, mass, and friction of the low speed mirror, an actuator that oscillates the low speed mirror cannot immediately oscillate the low speed mirror back to its original position. Thus, the contour of the amplitude of the oscillation of the slow mirror will have a rise / fall time 'h' as shown in FIG. Typically, the amplitude of the oscillation of the slow mirror will have a rise time or fall time of 10% and fall time or rise time of 90%, respectively.

As shown in Fig. 4, if the rise time or fall time for driving the signal used to drive the oscillation of the slow mirror is too short or too long, then the stray oscillations 2 are transmitted to the slow mirror. Can be. Stray oscillations may be due to, for example, the rebound of the slow mirror. Moreover, since the low speed mirror is subject to low air damping, the step response of the low speed mirror will be affected by stray oscillations. Moreover, these stray oscillations will increase with decreasing air damping applied on the surface of the low speed mirror.

As shown in FIG. 5, stray oscillations 2 damage the projected image 3 seen on the display surface 5 as the parts of the projected image 3 appear brighter than the other parts. For example, FIG. 4 shows that the portion 3a of the projected image 3 appears brighter than the portion 3b of the projected image 3.

US patent application US2008204839 describes a system using a vertical scan wave W (for each period) comprising a sawtooth wave Wa portion followed by a correction wave portion Wb. Scanning waves are applied to the reflective surface. Disadvantageously, the scanning wave requires a correction portion to suppress stray oscillations of the reflecting plate caused when the sawtooth wave immediately returns from the maximum level to the minimum level.

It is an object of the present invention to exclude or mitigate one or more of the above mentioned disadvantages.

According to a first aspect of the invention, there is provided a method, comprising: providing an optical signal configured to be projected onto a display surface for displaying an image; And oscillating the first reflective surface using an actuator operatively cooperating with the first reflective surface by applying the first drive signal to the first reflective surface to scan the optical signal across the display surface, A method of projecting an image is provided wherein the rise time or fall time of the first drive signal is inversely proportional to the resonant frequency of oscillation of the first reflective surface.

According to yet another aspect of the present invention, there is provided a method, comprising: providing an optical signal configured to be projected onto a display surface for displaying an image; And oscillating the first reflective surface using an actuator operatively cooperating with the first reflective surface by applying the first drive signal to the first reflective surface to scan the optical signal across the display surface, A method of projecting an image is provided wherein the rise time of the first drive signal is inversely proportional to the resonant frequency of oscillation of the first reflective surface.

According to yet another aspect of the present invention, there is provided a method, comprising: providing an optical signal configured to be projected onto a display surface for displaying an image; And oscillating the first reflective surface using an actuator operatively cooperating with the first reflective surface by applying the first drive signal to the first reflective surface to scan the optical signal across the display surface, A method of projecting an image is provided wherein the fall time of the first drive signal is inversely proportional to the resonant frequency of oscillation of the first reflective surface.

Providing a first drive signal having a rise time or fall time inversely proportional to the resonant frequency of oscillation of the first reflective surface ensures that stray oscillations are not transmitted on the first reflective surface. Moreover, since no stray oscillations are transmitted on the first reflective surface, this eliminates the need for a correction signal to suppress stray oscillations.

These methods include oscillating a second reflective surface about an oscillation axis using a second drive signal such that the first and second reflective surfaces oscillate with amplitudes of oscillation to scan an optical signal across the display surface. And the rise time or fall time of the first drive signal is inversely proportional to the resonant frequency of oscillation of the first reflective surface. The second reflective surface can be oscillated by applying a second drive signal to the second reflective surface using a second actuator in operative communication with the second reflective surface.

The method may further comprise filtering the first and / or second drive signals. The method may further comprise filtering the first drive signal. The method further includes filtering the first drive signal used to cause the oscillation of the first reflective surface to remove one or more frequency components from the first drive signal. The method further includes filtering the first drive signal used to cause the oscillation of the first reflective surface to remove any discontinuities in the first drive signal. Preferably, the filtered frequency components are within a frequency range window. The frequency range window can be defined by the user. The frequency range window may be centered at the resonant frequency of the reflective surface.

The method may further comprise compensating for a change in the position of the peak in the drive signal caused by the filtering.

The first and second reflective surfaces can be arranged to optically communicate with each other. The first and second reflective surfaces can be arranged to optically communicate with each other to direct light towards the display surface. The first reflective surface can be oscillated about the first oscillation axis and the second reflective surface can be oscillated about the second oscillation axis to scan light over the display surface. The first oscillation axis may be orthogonal to the second oscillation axis.

The first reflective surface can be configured to scan the light along a vertical reference. The second reflective surface can be configured to scan light along a horizontal reference. The first reflective surface can be oscillated to scan the light along a vertical reference. The second reflective surface can be oscillated to scan the light along a horizontal reference. Alternatively, the first reflective surface can be configured to scan light along a horizontal reference. The second reflective surface can be configured to scan the light along a vertical reference. The first reflective surface can be oscillated to scan light along a horizontal reference. The second reflective surface can be oscillated to scan the light along a vertical reference.

The first or second reflective surface may oscillate faster than the other reflective surface. The second reflective surface may oscillate faster than the first reflective surface. Thus, the second reflective surface can be a high speed reflective surface and the first reflective surface can be a low speed reflective surface.

The rise time or fall time may be an integer factor of 1 / F _resonant . Rise time or fall time may be as follows:

{1 / F _resonant } × N

Where F _resonant is the resonant frequency of the oscillation of the first reflective surface and N is the selected constant.

Rise time or fall time may be as follows:

{1 / (F _resonant ± f)} × N

Where F _resonant is the resonant frequency of oscillation of the first reflective surface, N is a selected constant, and f is a variable describing the filtering results of the first drive signal.

Preferably, the F _resonant is in the range of 1-5000 Hz. More preferably, the F _resonant is in the range of 100-2000 Hz. Most preferably, the F _resonant is in the range of 300-1000 Hz.

Preferably, N is in the range of 1-1000. More preferably, N is in the range 1-200. Most preferably, N is in the range 1-150. The parameter N is selected according to the desired mirror response.

Preferably, f is in the range of 0-500 Hz. More preferably, f is in the range of 1-400 Hz. Most preferably, f is in the range 1-250 Hz. The parameter f is linked to filtering which is empirically optimized according to the dynamic behavior of the reflective surface.

The reflective surface or each reflective surface can be a mirror. Preferably, the reflective surface or each reflective surface is a MEMS micromirror.

Are included in the scope of the present invention.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings,
1 is a graph showing the ideal amplitude of the oscillations of a slow mirror in a projector.
Fig. 2 is a graph showing the movement for the slow mirror progressing in sequential oscillation.
3 is a graph showing the actual amplitude of the oscillations of the slow mirror in the projector.
4 shows stray oscillations that may be caused on the slow mirror by oscillating the slow mirror very quickly or very slowly.
FIG. 5 shows how the projected image can be affected by the stray oscillations shown in FIG. 4.
6 provides a cross-sectional view of a projection device using high speed and low speed MEMS micromirrors to project an image onto a display surface.
FIG. 7 shows a drive signal applied to the low speed MEMS micromirror in the projection device of FIG. 6 to oscillate the low speed MEMS micromirror.
8 shows a filter signal that may be applied to filter the drive signal shown in FIG. 7.
FIG. 9 shows the drive signal of FIG. 7 after being filtered by the filter signal of FIG. 8 and shows the actual signal applied to the low speed MEMS micromirror to oscillate the low speed MEMS micromirror.

1-5 are described in the background of the section of the present invention.

6 provides a cross-sectional view of the projection device 1. The projection device 1 projects the 2-D image 130, with the result that the 2-D image is displayed on the display surface 10. Each individual pixel (not shown) of the 2-D image 130 is generated by combining modulated red 124, green 126, and blue 122 laser light sources by beam combiner 128. The combined modulated red 124, green 126, and blue 122 laser light is emitted from the beam combiner 128 as a pulsed light beam 4. Each pulse of the pulsed light beam 4 corresponds to a pixel of the 2-D image 130. The pulsed light beam 4 is directed towards the MEMS micromirror device 70. The MEMS micromirror device 70 directs this pulsed light beam 4 to the display surface 10 in turn, and the 2-D image 130 is represented pixel by pixel.

MEMS micromirror device 70 includes a first MEMS micromirror 103 and a second MEMS micromirror 105. The first MEMS micromirror 103 is oscillated about the first oscillation axis 9 to scan light along the horizontal, and the second MEMS micromirror 105 is configured to scan the light along the second oscillation axis. It oscillates about (11). The first MEMS micromirror 103 oscillates faster than the second MEMS micromirror 105, so that the first MEMS micromirror 103 is considered a high speed mirror and the second MEMS micromirror 105 is considered a slow mirror. do. The first MEMS micromirror 103 will hereinafter be referred to as the 'high speed mirror' 103 and the second MEMS micromirror 105 will hereinafter be referred to as the 'low speed mirror' 105. A first actuator (not shown) is used to operatively cooperate with the slow mirror 105 and to oscillate the slow mirror 105; A second actuator (not shown) is used to operatively cooperate with the high speed mirror 103 and to oscillate the high speed mirror 103.

The low speed mirror 105 and the high speed mirror 103 are arranged in the MEMS micromirror device 70 such that the first oscillation axis 9 is orthogonal to the second oscillation axis 11.

During operation, the high speed mirror 103 receives the pulsed light beam 4 from the beam combiner 128 through the first window 115 of the MEMS micromirror device 70, and the pulsed light beam 4 ) Is deflected on the reflective surface 121 in the MEMS micromirror device 70. Reflecting surface 121 in turn deflects pulsed light beam 4 to slow mirror 105. The slow mirror 105 deflects the pulsed light beam 4 in turn onto the display surface 10 through the second window 107 of the MEMS micromirror device 70, and within the pulsed light beam 4. Each pulse will appear as a pixel on the display surface 10.

The high speed mirror 103 in the MEMS micromirror device 70 will be oscillated about the first oscillation axis 9 to scan the pulsed light beam 4 along the horizontal. Since the high speed mirror 103 is oscillated, the low speed mirror 105 will also be oscillated slowly to scan the pulsed light beam 4 along the horizontal. The combined result of the oscillation of both the high speed and low speed mirrors 103, 105 results in the pulsed light beam 4 being scanned in a zigzag pattern across the display surface 10, thereby producing a 2-D image 130. The pixel by pixel on the display (10).

When all of the pixels of the 2-D image 130 have been displayed, light needs to be scanned again across the display surface 10 to reproduce the 2-D image 130. To reproduce the 2-D image 130, the light must once again be directed towards the starting point of the image (ie the point on the display surface 10 at which the very first pixel of the 2-D image 130 is displayed). As a result, scanning can begin from the beginning of the 2-D image 130 and the entire 2-D image 130 can be reproduced. The slow mirror 105 has a second oscillation axis 11 such that the pulsed light beam 4 is directed once more towards the point on the display surface 10 where the very first pixel of the 2-D image 130 is displayed. Oscillates back to its original position. The high speed mirror 103 and the low speed mirror 105 again oscillate their oscillation axes 9, 11 to scan the pulsed light beam 4 in a zigzag pattern across the display screen 10, thereby causing 2-D Will play the image 130. The process of scanning and playing the 2-D image 130 is performed at a speed that ensures that the continuous, complete 2D image 130 is shown to the viewer on the display surface 10.

The first actuator (not shown) is operatively in communication with the low speed mirror 105 and the second actuator (not shown) is operatively cooperating with the high speed mirror 103. The actuators may take any suitable form, for example the actuators may be piezoelectric, magnetic, electrostatic, thermal, or electromagnetic actuators. A first actuator (not shown) is used to cooperate with the slow mirror 105 and to launch the slow mirror 105; During operation, the first drive signal is applied to the low speed mirror 105 by the first actuator to oscillate the low speed mirror 105. The rise time (or fall time) of the first drive signal is inversely proportional to the resonant frequency of oscillation of the low speed mirror 105. A second actuator (not shown) is used to cooperate with the high speed mirror 103 and to oscillate the high speed mirror 103; During operation, a second drive signal is applied to the high speed mirror 103 by the second actuator to oscillate the high speed mirror 103. The second drive signal is configured to oscillate the high speed mirror 103 at a frequency of oscillation equal to the resonant frequency of the high speed mirror 103.

As discussed in the background art, in particular with reference to FIG. 4, if the rise time (or fall time) of the drive signal for driving the slow mirror 105 is too short or too long, then the stray oscillations may be caused by the slow mirror 105. Can be delivered to the phase. Thus, when reproducing the projected 2-D image 130, stray oscillations are transmitted on the slow mirror 105 when the slow mirror 105 oscillates back toward the starting point of the original 2-D image 130. There is a risk to be.

In order to prevent stray oscillations transmitted on the low speed mirror 105, the first drive signal applied to the low speed mirror 105 has a rising time 'h' (or falling) inversely proportional to the resonant frequency of the oscillation of the low speed mirror 105. Time). Providing such a drive signal ensures that the first actuator oscillates the slow mirror 105 at an optimum speed of oscillation that prevents stray oscillations transmitted on the slow mirror 105. The first drive signal has a rise time (or fall time) 'h' as shown below:

{1 / F _resonant } × N

Where F _resonant is the resonant frequency of the oscillation of the slow mirror 105 and N is the selected constant. Parameter N is selected empirically and in accordance with the desired slow mirror oscillation; For example, N may be equal to 1 or 2.

FIG. 7 illustrates a first drive signal applied to the low speed mirror 105 by a first actuator in the projection device of FIG. 6 to oscillate the low speed mirror. The first driving signal may be a current signal or a voltage signal. 7 graphically shows that the rise time (or fall time) 'h' of the first drive signal is as follows:

{1 / F _resonant } × N

In the particular first drive signal shown in FIG. 7, it will be appreciated that F _resonant is 750 Hz, but F _resonant may be any frequency in the range of 1-5000 Hz. In this particular example, it will be understood that N is equal to 200, but N may be any integer in the range of 1-1000. Thus, in order to oscillate the slow mirror 105 at the optimum speed to ensure that no stray oscillations are transmitted on the slow mirror 105, the first drive signal applied to the slow mirror 105 is given by the equation It should have a rise time 'h':

{1/750} × 200 = 0.266 sec

Ensuring that the rise time of the first drive signal is inversely proportional to the resonant frequency of the oscillation of the low speed mirror 105 ensures that stray oscillations (as shown in FIG. 4) are not transmitted on the low speed mirror 105. do.

As is apparent from FIG. 7, the first drive signal applied to the slow mirror 105 to oscillate the slow mirror includes a discontinuity at point “A”. This discontinuity has the potential to deliver stray oscillations on the slow mirror 105. Therefore, in order to achieve the optimum oscillation of the low speed mirror 105, the discontinuity at point 'A' must be removed before being applied to the low speed mirror 105.

To remove the discontinuities at point "A", the filtering signal is applied to the first drive signal. The filtering signal is shown graphically in FIG. 8; The filter providing this filtering signal is a cutband filter centered at the _resonant frequency F _resonant of the slow mirror 105. Upon application of the first drive signal, the filtering signal smoothes the drive signal at point 'A' such that discontinuities are eliminated.

9 shows the first drive signal of FIG. 7 after being filtered by the filter signal of FIG. 8. As is apparent from FIG. 9, the discontinuity at point "A" has been eliminated, but the peak B of the first drive signal is shifted to position C as a result of the filtering. To explain the movement at peak B, the rise time (or fall time) of the first drive signal is such that the rise time (or fall time) of the first drive signal actually applied to the slow mirror 105 is proportional to the following equation. Further adjustment is made by adding (or subtracting) the variable f to the F _resonant variable:

{1 / (F _resonant ± f)} × N

Typically, f is in the range 0-500 Hz. More preferably, f is in the range of 1-400 Hz. Most preferably, f is in the range 1-250 Hz. f may be used in determining an appropriate drive signal for a group or for a group of slow mirrors 105 to account for a variation in the resonant frequency within the group or for a batch of slow mirrors 105.

Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined in the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments.

Claims (15)

Providing an optical signal configured to be projected onto a display surface for displaying an image; And
The first using an actuator operatively cooperating with the first reflective surface by applying a first drive signal to the first reflective surface to scan the optical signal across the display surface Oscillating the reflective surface;
And a rise time or fall time of the first drive signal is inversely proportional to the resonant frequency of oscillation of the first reflective surface. The method of claim 1,
Oscillating a second reflective surface using a second drive signal such that the first and second reflective surfaces oscillate with amplitudes of oscillation to scan an optical signal across the display surface. 3. The method of claim 2,
And the second reflective surface is oscillated at a frequency that is a resonant frequency of the second reflective surface. The method according to any one of claims 1 to 3,
And filtering the first drive signal. 5. The method of claim 4,
Compensating for a change in the position of the peak in said first drive signal caused by filtering. 6. The method according to any one of claims 2 to 5,
And the first and second reflective surfaces are arranged to be in optical communication with each other. 7. The method according to any one of claims 2 to 6,
And the first reflective surface oscillates more slowly than the second reflective surface. The method according to any one of claims 1 to 7,
And the first reflective surface is configured to scan light along a horizontal reference. The method according to any one of claims 1 to 7,
And the first reflective surface is configured to scan light along a vertical reference. 10. The method according to any one of claims 1 to 9,
And the reflective surface or each reflective surface is a mirror. 11. The method according to any one of claims 1 to 10,
_Wherein said rise time or fall time is an integer factor of 1 / F _resonant and F _resonant is a resonant frequency of oscillation of said first reflective surface. 12. The method according to any one of claims 1 to 11,
The rise time or fall time is equal to {1 / (F _resonant ± f)} × N, where F _resonant is the resonant frequency of oscillation of the first reflective surface, N is a selected constant, f is the drive signal And / or a variable that compensates for the filtering results of and / or compensates for a variation in the resonant frequency within a batch of first reflective surfaces. 13. The method according to claim 11 or 12,
F _resonant is an image projection method in the range of 1 to 5000 Hz. The method according to claim 12 or 13,
N is an image projection method in the range of 1 to 1000. 15. The method according to any one of claims 12 to 14,
f is an image projection method in the range of 0 to 500 Hz.

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